1. Field of the Invention
The present invention relates to a magnetic recording medium, and more particularly to improvement of security.
The invention can be applied to a magnetic recording medium requiring illegal use preventing function and forgery and altering preventing function, for example, a magnetic card or the like.
2. Description of the Prior Art
In the prior art, such method is adopted that codes for discriminating truth or falsehood are formed on a part of a magnetic card, and read by a magnetic head so as to discriminate truth or falsehood thereby the security of the card is improved.
In the magnetic card of the prior art, such codes for discriminating truth or falsehood are formed by magnetic print patterns and non-magnetic dummy print patterns so that the codes cannot be easily deciphered. Material of high coercive force, such as magnetite (Fe.sub.3 O.sub.4) or maghemite (.gamma.-Fe.sub.2 O.sub.3), is used as material for the magnetic print pattern.
In the magnetic recording medium in the prior art, however, if external magnetic field is applied to read the codes for discriminating truth or falsehood, residual magnetization is produced in the magnetic print patterns thereby the codes for discriminating truth or falsehood can be visualized using a magnetic viewer or the like on the market.
In order to solve the problem, after the external magnetic field is applied for the reading or the like, it must be demagnetized every time resulting in complication of the system.